JPH0148068B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently removing paint adhering to an object other than the object to be painted (hereinafter referred to as a non-painted object) during a painting process. It is something.

Currently, in the coating industry, various coating methods including electrostatic coating have been established in terms of coating principles, and many technological advances have also been made in coating equipment. These technological developments have led to significant improvements in the appearance of the object to be coated and in so-called painting workability, including painting work efficiency; however, there are still problems in the painting process that require various solutions. The current situation is that only a few points remain. Such problems include the various guides and equipment used near the object to be coated during painting, or the general equipment used to prevent unnecessary diffusion of paint. Paint that inevitably adheres to fixtures, such as so-called paint booths, can accumulate during repeated use of such tools, equipment, or fixtures. Such paint deposits cause a great deal of trouble in painting operations, such as by falling during painting operations. Therefore, it is necessary to remove paint deposits before they accumulate to an extreme thickness, but in order to remove them, for example, it is necessary to apply a large impact force to the paint deposits many times, and it is necessary to completely remove the paint deposits. It is extremely difficult to remove it. Moreover, as the non-painted object itself is damaged in various sizes by such removal work, the smoothness of the surface is lost, which makes it even more difficult to remove the adhered and deposited paint, which reduces the efficiency of the entire painting process. It has decreased significantly.

To give a concrete example of the troubles in painting work caused by the paint deposits mentioned above, in the spray painting process or dip painting process, the object to be painted is generally hung on a hanger, and in the case of automobile bodies. The object to be coated goes through the painting process while being supported by some kind of support, such as being painted on a cart called a trolley. At this time, the paint that inevitably adheres to such supports such as hangers and carts accumulates while the supports are used repeatedly. If the paint is deposited to an extreme thickness, some of the deposited paint may be affected by vibrations that occur during the painting process (for example, vibrations caused by the running of the paint line or collisions with the supporting body such as a trolley). Vibrations, etc. caused by the coating may cause the paint to fall onto the running path of the painting line, causing trouble in running, or fall onto the surface of the object to be coated, significantly impairing the appearance of the object. Furthermore, in the case of electrostatic coating, paint deposited on the support or the inner surface of the coating booth generates a charge repulsion force, which impairs the appearance of the surface of the object to be coated.

Therefore, how to efficiently remove paint adhering to non-painted objects such as supports of objects to be painted and painting booths is an important concern for painting process managers, and solutions are needed. This is a problem.

In view of this situation, the present inventors provide a method for most effectively removing paint adhering to non-painted objects.

That is, the present invention involves emulsion polymerization of one or more unsaturated monomers capable of radical polymerization onto the surface of the non-painted object in advance when removing the paint adhering to the non-painted object in the painting process. A film-forming substance consisting of an aqueous polymer dispersion obtained by is applied and dried to form a film,
The present invention relates to a method for removing paint adhering to a non-painted object, characterized in that the paint adhering to the coating is removed by peeling it off from the surface of the coating.

The effect obtained by carrying out the method of the present invention is that by applying the specific film-forming substance of the present invention to the surface of a non-painted object to form a film, the paint adhering to the film is extremely Until it is deposited to a certain thickness, it will not fall off due to the various vibrations that normally occur during the coating process. However, when removing this, a significantly lower impact force is applied fewer times than when attempting to remove paint deposits that have formed without the application of a film-forming substance. It becomes possible to peel it off from the surface and remove it easily and completely. Furthermore, since the coating and the non-painted object itself are hardly damaged by such removal operations,
Once the film-forming substance of the present invention is applied to a non-painted object to form a film, the film can be removed without applying the film-forming substance again after removing the paint deposits that have adhered to the film. The operation of removing paint deposits adhering to the top can be carried out repeatedly with almost the same ease.

As is clear from these effects, by implementing the method of the present invention, the efficiency of the entire coating process can be significantly improved.

Next, the aqueous polymer dispersion used as a film-forming substance in the present invention will be described.

Examples of radically polymerizable unsaturated monomers that can be used to obtain the aqueous polymer dispersion used in the present invention include aliphatic unsaturated hydrocarbons such as ethylene and butadiene; Halogen substituted products of saturated hydrocarbons; Aromatic unsaturated hydrocarbons such as styrene and divinylbenzene; Unsaturated carboxylic acids and their esters such as acrylic acid, methacrylic acid, and maleic acid; Vinyl esters such as vinyl acetate Vinyl ethers; Allyl alcohol and its esters with various organic acids and ethers with various alcohols; Unsaturated cyanide compounds such as acrylonitrile, etc., and one or more selected from these groups can be used. Among these unsaturated monomers, α,β-ethylenically unsaturated monomers are preferably used. More preferably, the α,β-ethylenically unsaturated monomer used does not have any reactive groups other than unsaturated groups, and is particularly preferably selected from acrylic esters, methacrylic esters, acrylonitrile, and methacrylonitrile. It is preferable to use one or more selected monomers in an amount of 50% by weight or more based on the total unsaturated monomers used. Furthermore, the emulsion polymerization for obtaining the aqueous polymer dispersion in the present invention can basically be carried out according to conventionally known methods. That is, in an inert atmosphere, under autogenous or artificially induced pressure, in a closed container or in an open container under atmospheric reflux, in the presence or absence of an emulsifier, in the presence of water, in the presence of a polymerization catalyst. An aqueous polymer dispersion can be obtained by emulsion polymerization of one or more unsaturated monomers in the presence or absence of a monomer.

Among these aqueous polymer dispersions, there are some with different glass transition temperatures in terms of film-forming properties, film properties such as film flexibility, toughness, and temperature change resistance, and workability for removing adhered paint deposits. A polymer obtained by sequential emulsion polymerization of two or more monomer components is preferred. Note that the order of addition of these monomer components is not particularly limited. More preferably, the difference in glass transition temperature between the monomer component that yields a polymer with the highest glass transition temperature and the monomer component that yields a polymer with the lowest glass transition temperature is 30
It is desirable that the temperature is above ℃. More preferably,
The monomer component that yields the polymer with the highest glass transition temperature and the monomer component that yields the polymer with the lowest glass transition temperature are both based on the total amount of all monomer components. It is desirable that the content is 10% by weight or more.

Furthermore, as the polymerizable aqueous dispersion, a mixture of two or more types of polymerizable aqueous dispersions containing polymers having different glass transition temperatures is also preferable. The difference in glass transition temperature between the polymerizable aqueous dispersion containing the polymer with the highest glass transition temperature and the polymerizable aqueous dispersion containing the polymer with the lowest glass transition temperature is 30°C or more. , more preferred.

The glass transition temperature referred to in this specification is expressed by the following general formula.

However, Tg: Glass transition temperature of the copolymer (〓) Wi: Weight fraction of each unsaturated monomer constituting the copolymer Tgi: Homopolymer of each unsaturated monomer constituting the copolymer glass transition temperature (〓).

n: number of unsaturated monomers used.

Conventionally known emulsifiers can be used in emulsion polymerization to obtain the aqueous polymer dispersion used in the present invention. Examples of anionic emulsifiers include fatty acid salts, higher alcohol sulfate ester salts, alkylbenzene sulfonates, alkylnaphthalene sulfonates, naphthalene sulfonic acid formalin condensates, dialkyl sulfosuccinate ester salts, polyoxyethylene alkyl sulfosuccinate monoester salts, Oxyethylene alkyl sulfate salts, polyoxyethylene alkylaryl sulfate salts, polyoxyethylene alkyl phosphate salts, etc.; nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid ester,
polyoxyethylene sorbitan fatty acid ester,
Examples include oxyethylene oxypropylene block copolymers and fatty acid monoglycerides. One or more emulsifiers selected from the group of such emulsifiers can be effectively used, and the amount used is preferably in the range of 0.1 to 10% by weight based on the total unsaturated monomers. Note that, if necessary, protective colloids can be used alone or together with an emulsifier, and furthermore, in some cases, it is also possible to obtain an aqueous polymer dispersion without using these emulsifiers or protective colloids at all. Polymerization catalysts for emulsion polymerization of unsaturated monomers include inorganic peroxides such as ammonium persulfate and hydrogen peroxide; organic peroxides such as t-butyl hydroperoxide; and other radical-generating polymers. An initiator or the like may be used, and the amount used is 0.01 to 3 parts by weight, preferably 0.1 to 1 part by weight, per 100 parts by weight of the unsaturated monomer. When using peroxide,
If it is necessary to increase the polymerization rate or lower the reaction temperature, redox can be used in combination with peroxides, reducing agents such as soluble sulfites or ascorbic acid, or metal compounds that generate heavy metal ions in water such as ferrous sulfate. It can be a system.

The emulsion polymerization temperature is appropriately selected depending on the type and composition of the unsaturated monomer, the type of polymerization catalyst, etc.
It is usually in the range of 0 to 100°C.

The amount of water during emulsion polymerization is usually 100% of the unsaturated monomer.
The ratio is 300 to 50 parts by weight.

The obtained aqueous polymer dispersion can be effectively used as the film-forming substance of the present invention as it is, or after adjusting the pH to a desired range by adding a pH regulator consisting of a base or acid as necessary. However, if necessary, various additives such as thickeners, anti-sagging agents, flow control agents, plasticizers, film-forming aids, rust preventives, antifoaming agents, release agents, pigments or dyes may be added. It can also be added as appropriate to form a film-forming substance.

The film-forming substance thus obtained is applied to a non-painted object before the paint is attached or to a non-painted object from which the paint has been removed, by a method such as brush painting, spray painting, roller painting or dip painting, By drying at room temperature or under heating depending on the minimum film-forming temperature of the film-forming substance, an effective film can be formed on the surface of a non-coated object.

By carrying out the method of the present invention, it is possible to carry out the removal work in the painting process very efficiently to avoid problems caused by paint that inevitably adheres and accumulates on non-painted objects, and therefore the entire painting process can be carried out very efficiently. efficiency can be significantly increased.

Although it is not possible to determine the reason why the method of the present invention produces such effects, it is generally recognized that emulsion polymerization can produce extremely high molecular weight polymers, and the molecules of such polymers are When a film is formed from the dispersion, they flow together and adhere with some degree of strength to the surface of the non-coated object to which the aqueous dispersion has been applied, forming a continuous and tough film. Even after a paint containing various components adheres to the film and the paint goes through the process of drying or curing, the high molecular weight polymer that makes up the film only sticks to the paint weaker than it does to non-painted objects. It is presumed that this is due to not doing so.

Therefore, any unsaturated monomer for obtaining the aqueous polymer dispersion used in the present invention can be effectively used as long as it is capable of radical polymerization. α,β-ethylenically unsaturated monomers that give polymers that do not contain unsaturated bonds that are susceptible to change, especially those that contain various reactive groups that may interact with various components of the paint to which they are attached. It is preferred to use α,β-ethylenically unsaturated monomers which give polymers with no Among these α,β-ethylenically unsaturated monomers, acrylic esters, methacrylic esters, acrylolitrile, and methacrylic esters provide polymers that are chemically relatively stable and capable of forming a strong film. It is preferable to use nitrile as a main component.

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, in Examples and Comparative Examples, parts indicate parts by weight, and % indicates weight %.

Example 1 135.6 parts of deionized water was charged into a glass flask equipped with a stirrer, a thermometer, a dropping funnel, a nitrogen gas inlet, and a reflux condenser, and the flask was purged with nitrogen.
The temperature was then raised to 50°C, and dodecylbenzene was added to 48.0 parts of a mixture of 11.5 parts of methyl methacrylate and 36.5 parts of butyl acrylate (the calculated glass transition temperature of the polymer obtained by copolymerizing this mixture was -32°C). An unsaturated monomer emulsion dispersion obtained by adding 0.48 parts of sodium sulfonate, 1.92 parts of polyoxyethylene nonyl phenyl ether, and 16.0 parts of deionized water and stirring and mixing was added, and the mixture was heated at 50°C for 10 minutes. Mixing and stirring were performed.

Thereafter, 5 parts of a 20% aqueous solution of ammonium persulfate and 1.5 parts of a 10% aqueous solution of sodium hydrogensulfite were added to initiate polymerization. After polymerization starts
After 20 minutes, sodium dodecylbenzenesulfonate was added to 49.0 parts of a mixture of 17.8 parts of methyl methacrylate and 31.2 parts of butyl acrylate (the calculated glass transition temperature of the polymer obtained by copolymerizing this mixture is -17°C). 0.49 parts of polyoxyethylene nonyl phenyl ether, 1.96 parts of deionized water, and 16.3 parts of deionized water.
% aqueous solution was continuously added over 40 minutes while maintaining the reaction temperature at 60° C. to advance emulsion polymerization. Then, after continuing to mix and stir at 60°C for 10 minutes, a mixture of 26.0 parts of methyl methacrylate and 22.0 parts of butyl acrylate (the calculated glass transition temperature of the polymer obtained by copolymerizing this mixture is 8°C) 48.0 0.48 parts of sodium dodecylbenzenesulfonate, 1.92 parts of polyoxyethylene nonyl phenyl ether, and 16.0 parts of deionized water were added and mixed with stirring. 10% aqueous solution
1.5 parts of each while maintaining the reaction temperature at 60°C.
Polymerization was allowed to proceed by continuous addition over 40 minutes. Then, after continuing to mix and stir at 60°C for 10 minutes, 35.7 parts of methyl methacrylate and 19.3 parts of butyl acrylate were added.
(The calculated glass transition temperature of the polymer obtained by copolymerization of this mixture is 26℃) 55.0
Sodium dodecylbenzenesulfonate 0.55 parts
Part, polyoxyethylene nonyl phenyl ether
An unsaturated monomer emulsion dispersion obtained by adding 2.20 parts and 18.3 parts of deionized water and stirring, and 1.5 parts of a 10% aqueous solution of sodium hydrogen sulfite,
While maintaining the reaction temperature at 60°C, each addition was continued for 40 minutes to allow polymerization to proceed. Then 60
Mixing and stirring was continued for 60 minutes at °C to complete polymerization, and an aqueous polymer dispersion was obtained. Next, to 100 parts of the obtained aqueous polymer dispersion, 0.1 part of 28% aqueous ammonia was added to adjust the pH to 9, and 5 parts of a 10% aqueous solution of ammonium benzoate as a rust preventive agent was added to make the solution uniform. The mixture was mixed and stirred using a spray gun and applied to a trolley used in an automobile painting line (made of iron with no paint deposits), and dried for about 2 hours at 25°C in an atmosphere with a relative humidity of 60%. A transparent, uniform coating was formed on the surface of the truck.

For comparison purposes, carts that had not been coated and carts that had been coated were repeatedly used on an automobile painting line where a thermosetting acrylic resin paint was applied by spray and then subjected to a heating drying process. The thickness of the paint deposited on the trolley is 0.5 to 1.0 cm.
At that point, we took out the two types of carts and removed the paint deposits by hitting them with a hammer.

A part of the paint deposits on the trolley that had been coated on it will be easily peeled off from the surface of the coat by tapping it lightly several times with a hammer, and about 20 minutes after starting the removal process, the paint will be removed. All of the deposits were completely removed. Moreover, the coating that had been formed on the truck was hardly damaged. After this removal operation, the cart was repeatedly used in the same painting line as described above, and even when the same removal operation was performed, almost the same effect as in the first case was obtained. On the other hand, in the case of the truck to which the film-forming substance of the present invention is not coated, it is necessary to hit it strongly with a hammer more than 10 times to remove even a small portion of the paint deposit, and most of the paint deposit is removed. It took more than two hours to complete, and the truck was left with damage of various sizes. After this work was completed, the trolley was repeatedly used on the same painting line as above, and then the same removal work was performed, but the work was even more difficult than the first time, and the damage to the trolley was also greater. Ta.

Example 2 135.1 parts of deionized water was charged into the same flask as used in Example 1, and the flask was replaced with nitrogen. Then
Unsaturated product obtained by heating to 50°C, adding 6.0 parts of polyoxyethylene alkyl sulfate ammonium salt and 66.7 parts of deionized water to a mixture of 160 parts of ethyl acrylate and 40 parts of acrylonitrile, and stirring and mixing. Of 272.7 parts of monomer emulsion dispersion
27.3 parts were added and mixed and stirred at 50°C for 10 minutes. Then a 20% aqueous solution of ammonium persulfate 3
1 part and 0.3 parts of a 10% aqueous solution of sodium bisulfite were added to initiate polymerization. 15 minutes after the start of polymerization, the remaining 245.4 parts of the unsaturated monomer and 2.7 parts of a 10% aqueous solution of sodium sulfite were added.
While maintaining the reaction temperature at 60°C, each was added continuously for 180 minutes to advance emulsion polymerization. Then, mixing and stirring were continued for 60 minutes at 60°C to complete polymerization, and an aqueous polymer dispersion was obtained.

Next, for 100 parts of the obtained aqueous polymer dispersion,
Add 0.07 part of 28% ammonia water to adjust the pH to 9.
Furthermore, 5 parts of a 10% aqueous solution of ammonium benzoate as a rust preventive agent and 1 part of a 10% aqueous solution of polyvinyl alcohol with a degree of saponification of 87 to 89 mol% as a thickener were added, and the mixture was uniformly mixed and stirred to reduce the viscosity to approximately A concentration of 3000 centipoise was applied with a brush to a hanger (made of iron without any paint deposits) used for hanging metal furniture in a metal furniture dip coating line, and the relative humidity was maintained at 25°C. After drying in a 60% atmosphere for about 2 hours, a transparent and uniform film was formed on the surface of the hanger.

For comparison, hangers that had not been coated and hangers that had been coated were repeatedly used on a coating line where a water-soluble alkyd resin paint was mainly applied by dip coating and then passed through a heating drying process. When the thickness of the paint deposited on the hangers reached approximately 0.5 cm, the two types of hangers were removed and the deposits of paint adhered to them were removed by hitting them with a hammer.

If a coat has been formed on the hanger, some of the paint deposits will be easily peeled off from the surface of the coat by tapping it lightly with a hammer several times, and all of the paint deposits will be removed in about 10 minutes. has been completely removed. Moreover, the coating on the hanger that had been formed in advance was hardly damaged. and,
After this removal operation, the hanger was used again in the same painting line as described above, and even when the same removal operation was performed, almost the same effect as in the first case was obtained. On the other hand, with the hanger of the present invention, which is not coated with a film-forming substance, it is necessary to hit it strongly with a hammer more than 10 times to remove even a small portion of the paint deposits, and most of the paint deposits are removed. It took more than an hour to do so, and the hanger was left with damage of various sizes. After this removal process, the hanger was used again on the same painting line as described above, and when the same removal process was performed, the process was even more difficult than the first time, and the extent of damage to the hanger was also increased. .

Claims (1)

[Claims] 1. Objects other than objects to be painted in the painting process (hereinafter referred to as non-painted objects)
When removing paint adhering to the surface of a non-painted object, an aqueous polymer dispersion obtained by emulsion polymerization of one or more radically polymerizable unsaturated monomers is applied to the surface of the non-painted object in advance. A film-forming substance is applied and dried to form a film,
A method for removing paint adhering to a non-painted object, the method comprising removing the paint adhering to the coating by peeling it from the surface of the coating. 2. The paint according to claim 1, wherein the aqueous polymer dispersion is obtained by sequential emulsion polymerization of two or more monomer components that yield polymers with different glass transition temperatures. How to remove. 3. The method for removing paint according to claim 1, wherein the aqueous polymer dispersion is a mixture of two or more aqueous polymer dispersions containing different polymers having different glass transition temperatures.